trivial bash skill

* awk 使用shell变量
  ls *.rpm | sort | awk '{print $1 " '${linenum}'"}'

* float number
  # echo "scale=3; 13 / 3" | bc
  4.333

* argc
  f()
  {
        echo "$# args"
  }
  func()
  {
        f "$*"
        f "$@"
  }
  func a b c
  # sh argc.sh
  1 args
  3 args

* rmdir link
  # ln -s 090903-215949 latest
  # ls
  090903-215949 latest
  # rm latest/
  rm: cannot remove directory `latest/': Is a directory
  # rm -rf latest/
  rm: cannot remove `latest/': Not a directory

* sed
1，只输出，不保存：
[root@RHEL5GA ~]# PDES="[tcsh] fix a manual bug about 'Pmode:'"
[root@RHEL5GA ~]# echo "${PDES}" | sed "s/'/\\\'/g"
[tcsh] fix a manual bug about \'Pmode:\'

使用3个，\\\

2，如果要保存为变量：
PDES="[tcsh] fix a manual bug about 'Pmode:'"
echo "${PDES}"
PDES=`echo "${PDES}" | sed "s/'/\\\\\